This invention relates to a grabbing device of the type carried by an arm or boom of an excavating machine or the like.
SE-A 7900040-0 and 7714027-5 disclose grabbing devices or means directly attached to an excavating bucket. Grabbing arms attached to an excavating bucket--symmetrically grabbing as according to the first mentioned publication or grabbing otherwise--make it possible to use the excavator bucket for grabbing and lifting of objects, e.g., pipes, poles and the like. As the grabbing arms are arranged at the rear side of the bucket, the bucket must be swung into a back position before the grabbing arms can be brought to engage, say, a pipe lying on the ground, resulting in the grabbing area being concealed to the operator by the bucket. Furthermore, the machine arm will be constantly biassed by the weight of the bucket as well as by that of the grabbing device. As a medium size bucket may have a weight of 1,000 kgs or more, it is easily seen that already on idling very heavy weights are handled.
It also must be noted that today a large number of bucket types are available, e.g., narrow buckets for pipe or cable trench digging, wide ones for light material handling, buckets with a V-shaped bottom and a variety of other special types. It is in no way so that the demand for a grabbing device is restricted and related to a specific bucket type.
Another aspect in connection with grabbing devices directly mounted at a bucket is that the bucket and the grabbing device hardly can be expected to have the same service life. As a rule the bucket will be worn out earlier and then the choice would be between repeatedly repairing the bucket far beyond the normal and economically motivated limit in order to have an at least passably functioning carrier for the grabbing device, or discarding or scrapping the grabbing device prematurely together with the bucket.
A bucket equipped with grabbing arms but otherwise arranged in a conventional manner is, in the same way as ordinary buckets, only movable relative to the excavator arm about a transversely arranged axis and this fact results in that, in order to grab, e.g, a pipe positioned more or less tangentially relative to the center of pivot of the excavator, the entire machine must be operated and moved s that the vertical pivot plane of the arm becomes essentially parallel with the longitudinal direction of the pipe. This, naturally, involves a waste of time and in many instance makes the grabber arms useless, resulting in that lifting slings, chains or the like have to be used for changing the position of the object to be lifted.
Besides the fact that the operator's view is obstructed by the bucket of the known systems and grabbing ca take place in certain positions only, the possibilities for orienting a lifted object into a given position or moving the same toward a predetermined mounting position are extremely limited. Without moving the excavator itself, displacement of objects is possible only in the direction of the arm or boom in known machine arrangements.
SE-A-8901884-0 discloses a device adapted to be intercoupled between an excavator boom or arm and a bucket or the like tool, and such device is so arranged as to allow turning of the bucket around an axis oriented essentially in the length direction of the boom and tilting around an axis in the plane of movement of the boom. By this arrangement, the bucket may be made to work sideways or obliquely and may furthermore be tilted relative to the boom in order to make possible digging at slopes and the like in spite of the fact that the excavator machine stands in position in which conventional bucket connecting means would make digging quite impossible.
In the device according to this invention, a similar rotation and tilting apparatus is utilized for a quite new purpose.